You activate the effect of “Sasuke Samurai #4” at the beginning of the Damage Step, before the monster is flipped face-up. A monster destroyed by the effect of “Sasuke Samurai #4” is not destroyed as a result of battle. There is no damage calculation. It is not flipped face-up. Any Flip Effects it has are not activated.
If “Sasuke Samurai #4” attacks a face-up Attack Position “Reflect Bounder”, the effect of “Sasuke Samurai #4” is resolved before the effect of “Reflect Bounder”.